electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
Live streaming at radio.electro-music.com

  host / artist show at your time
<on air> mosc Sorry - program must be rescheduled for Monday at the same time.
Please visit the chat
 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Alien Screamer Noise Box question
Post new topic   Reply to topic Moderators: dnny, Uncle Krunkus, v-un-v
Page 1 of 1 [9 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
snivelsnot



Joined: Feb 14, 2013
Posts: 4
Location: Moscow

PostPosted: Thu Feb 14, 2013 12:39 am    Post subject: Alien Screamer Noise Box question
Subject description: a little help required please
Reply with quote  Mark this post and the followings unread

Hi all, I've just completed my first Alien Screamer Noise Box (http://www.musicfromouterspace.com/forums.html?MAINTAB=SYNTHDIY&PROJARG=ALIENSCREAMER/ALIENSCREAMER.php&CATPARTNO=ALIENSCREAMERPCB), but it doesn't work properly - it just produces low-frequency beat without any sighnificant high frequency modulation on it (http://imageshack.us/a/img201/9100/asnb.jpg), so I have a couple of questions:
1)Aluminium non polarized capacitors of a 1uF value are not available in the element stores, so what would be a better replace:
- 2 aluminium non polarized capacitors of a 2.2uF value, connected sequentially;
- a ceramic capacitor of a 1 uF value;
- a film capacitor of a 1 uF value?
2)A LM386N3 chip also doesn't appear to be available to buy (LM386N4 neither), so can I use a LM386N1 chip instead? As I have figured, it wouldn't affect the circuit in any way except lowering the speaker volume, which can be compensated by using a speaker with lower resistance (< 8 ohms).
I would appreciate any advice or correction, thanks in advance!
Back to top
View user's profile Send private message
elmegil



Joined: Mar 20, 2012
Posts: 1475
Location: Chicago
Audio files: 14

PostPosted: Thu Feb 14, 2013 6:11 am    Post subject: Reply with quote  Mark this post and the followings unread

Good luck finding a ceramic at 1uF! Smile

I would use ( and have ) the back to back electrolytics....

I don't usually work with LM386 chips at a detail that cares about N1/N3/N4 so perhaps someone else will be able to answer that.
Back to top
View user's profile Send private message
snivelsnot



Joined: Feb 14, 2013
Posts: 4
Location: Moscow

PostPosted: Fri Feb 15, 2013 2:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks a lot for the advice about capacitors, but do you think using the right ones can solve the modulation problem? Is the schematic presented on the web (http://www.musicfromouterspace.com/forums.html?MAINTAB=SYNTHDIY&PROJARG=ALIENSCREAMER/ALIENSCREAMER.php&CATPARTNO=ALIENSCREAMERPCB) correct after all?
Back to top
View user's profile Send private message
elmegil



Joined: Mar 20, 2012
Posts: 1475
Location: Chicago
Audio files: 14

PostPosted: Fri Feb 15, 2013 6:15 am    Post subject: Reply with quote  Mark this post and the followings unread

I have done a lot of troubleshooting of various Ray Wilson designs, and I have yet to find a mistake in his schematics.

You say "the right one", but you have not described what "the wrong one" might be, so I have no idea as to the cause of your beating problem.

In what ways have you deviated from the schematic?

Are you using Ray's PCB?
Back to top
View user's profile Send private message
snivelsnot



Joined: Feb 14, 2013
Posts: 4
Location: Moscow

PostPosted: Tue Feb 19, 2013 12:11 am    Post subject: Reply with quote  Mark this post and the followings unread

I've actually assembled the noise box twice - for the first time I was using a breadboard and wires and for the second time I printed a circuit board myself according to Ray's schematics. Both times the deviations from original circuit included using 1uF ceramic capacitors instead of non-polarized electrolitic ones (C4 and C12) and a LM386N1 chip instead of a LM386N3 (or 4) one. I've also simulated the work of the noise box in MicroCap9 but without the amplifier part (LMN386 chip is not present in MC9), the problem seems to be the same - the output signal appears to have no high frequency component. I'm attaching the pictures of the circuit I've built in MC9 and the output signal:
http://imageshack.us/a/img191/7821/asnbcircuit.jpg
http://imageshack.us/a/img201/9100/asnb.jpg
Once again thanks a lot for your interest in my little experiment! Wink

Last edited by snivelsnot on Tue Feb 19, 2013 2:48 am; edited 1 time in total
Back to top
View user's profile Send private message
analog_backlash



Joined: Sep 04, 2012
Posts: 391
Location: Aldershot, UK
Audio files: 21

PostPosted: Tue Feb 19, 2013 2:38 am    Post subject: Reply with quote  Mark this post and the followings unread

elmegil wrote:
Good luck finding a ceramic at 1uF! Smile

I assume that snivelsnot has used multilayer ceramics, which go up to (and above) 1uF. I've just been looking at the schematic and I don't see why 1uF multilayer ceramics shouldn't work and looking at the LM386 datasheet confirms that the only effect of using the LM386 N-1, would be to limit the output level. Looking at your scope trace, it is clear that the LFO is working, but the VCO is not. I can only guess that there's a problem in this part of the circuit, so I'd check that very carefully.

Since this is quite a small circuit, I'll try breadboarding it sometime today and see what happens. As elmegil says, Ray's circuits/PCBs are usually spot on, so it's unlikely (but not impossible) that there are mistakes in it.

Gary
Back to top
View user's profile Send private message
wayoda



Joined: Dec 04, 2012
Posts: 5
Location: Germany

PostPosted: Tue Feb 19, 2013 6:39 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi,
this post here
http://www.diyaudio.com/forums/parts/117452-non-polar-electrolytic-vs-polypropylene-film-capacitors.html
suggests that film-capacitors are an improvement to non-polarized elcos at least in audio circuits.

I also can't think of any (pyhsical) reason why a film-capacitor should not work here
Back to top
View user's profile Send private message
analog_backlash



Joined: Sep 04, 2012
Posts: 391
Location: Aldershot, UK
Audio files: 21

PostPosted: Tue Feb 19, 2013 12:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

Right. Finally got round to it. I breadboarded the circuit and it seems to work fine. There's an mp3 file attached. There are a few glitches, because I'm working on a breadboard and I've used preset pots, but basically, it seems OK. I tried changing the capacitors C4 and C12 and it worked on everything I put in, i.e.

1uF multilayer ceramics
2.2uF non-polarised electrolytics (I didn't have 1uF)
220nF mylar (ditto)
Two back-to-back 2.2uF polarised electrolytics (i.e. 1.1uF)

The example that I've posted uses the final combination, although all seemed to work pretty well.

I've also posted some waveforms. The left-hand side 3 traces are of the LFO waveforms (from the common of S2). These are as shown in Ray's schematic. The right-hand side traces are of the output waveform (from C12). The top one is unmodulated (a ramp), the middle is squarewave modulated and the bottom one is in sync mode.

These outputs are all before the amp stage. I had an LM386-N1, so I tried that and got quite a loud output, especially when I added the 10uF capacitor across pins 1 and 8 of the amp.

I think that this confirms that you have a problem in the VCO part of the circuit as you are only getting the low frequency output of the LFO. I'd check that part very carefully, as I don't think that there should be any problems with the components that you have used.

Gary

EDIT

Forgot to say that if you use a standard brightness LED, the output is a bit pathetic. I changed it the a bright blue one (not one of the really high brightness ones) and I got much better results. Also:

wayoda wrote:
Hi,
this post here
http://www.diyaudio.com/forums/parts/117452-non-polar-electrolytic-vs-polypropylene-film-capacitors.html
suggests that film-capacitors are an improvement to non-polarized elcos at least in audio circuits.

I also can't think of any (pyhsical) reason why a film-capacitor should not work here


Yes, I've read this before, but since this is basically a very lo-fi circuit, I didn't think that it would matter that much. Generally though, I think that the polypropylene film capacitors are a good idea.


Alien Screamer Waveforms.jpg
 Description:
 Filesize:  280.72 KB
 Viewed:  43 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

Alien Screamer Waveforms.jpg



Alien Screamer Test.mp3
 Description:

Download
 Filename:  Alien Screamer Test.mp3
 Filesize:  2.25 MB
 Downloaded:  105 Time(s)

Back to top
View user's profile Send private message
snivelsnot



Joined: Feb 14, 2013
Posts: 4
Location: Moscow

PostPosted: Wed Feb 20, 2013 11:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks a lot for such a detailed answer, from now on I'm sure the schematic is correct. I'll try check the quality of my components and soldering itself!
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic Moderators: dnny, Uncle Krunkus, v-un-v
Page 1 of 1 [9 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
e-m mkii

Please support our site. If you click through and buy from
our affiliate partners, we earn a small commission.


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use